Natural selection for the Duffy-null allele in the recently admixed people of Madagascar

While gene flow between distantly related populations is increasingly recognized as a potentially important source of adaptive genetic variation for humans, fully characterized examples are rare. In addition, the role that natural selection for resistance to vivax malaria may have played in the extreme distribution of the protective Duffy-null allele, which is nearly completely fixed in mainland sub-Saharan Africa and absent elsewhere, is controversial. We address both these issues by investigating the evolution of the Duffy-null allele in the Malagasy, a recently admixed population with major ancestry components from both East Asia and mainland sub-Saharan Africa. We used genome-wide genetic data and extensive computer simulations to show that the high frequency of the Duffy-null allele in Madagascar can only be explained in the absence of positive natural selection under extreme demographic scenarios involving high genetic drift. However, the observed genomic single nucleotide polymor...

尽管远缘种群间的基因流（gene flow）日益被认为是人类适应性遗传变异的潜在重要来源，但得到完整表征的此类案例仍较为罕见。此外，针对间日疟（vivax malaria）的抗性自然选择，是否在保护性达菲阴性等位基因（Duffy-null allele）的极端分布中发挥了作用，这一问题尚存争议：该等位基因在撒哈拉以南非洲大陆几乎完全固定，而在其他地区则完全缺失。我们通过对马达加斯加人群——这一兼具东亚与撒哈拉以南非洲大陆主要祖先成分的近期混合人群（admixed population）——的达菲阴性等位基因演化展开研究，以解决上述两个问题。本研究采用全基因组遗传数据（genome-wide genetic data）与大规模计算机模拟（computer simulations），结果表明，若假设不存在正向自然选择（positive natural selection），则马达加斯加境内达菲阴性等位基因的高频率仅能在涉及强烈遗传漂变（genetic drift）的极端人口统计学场景下得到解释。然而，观测到的基因组单核苷酸多态性……